1. Field of the Invention
The present invention relates to: an actinic ray-sensitive or radiation-sensitive resin composition suitable for use in the ultramicrolithography process such as production of VLSI or a high-capacity microchip or in other photofabrication processes; a resist film formed of the composition; a pattern forming method using the same; and a resin for use in the actinic ray-sensitive or radiation-sensitive resin composition. More specifically, the present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition for an electron beam, X-ray or EUV light, a resist film formed of the composition, a pattern forming method using the same, and a resin for use in the actinic ray-sensitive or radiation-sensitive resin composition.
2. Description of the Related Art
In the process of producing a semiconductor device such as IC and LSI, microprocessing by lithography using a photoresist composition has been conventionally performed. Recently, the integration degree of an integrated circuit is becoming higher and formation of an ultrafine pattern in the sub-micron or quarter-micron region is required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to i line or further to KrF excimer laser light. At present, other than the excimer laser light, development of lithography using an electron beam, an X ray or EUV light is proceeding.
The electron beam lithography is positioned as the next or next-next generation pattern formation technique, and a positive resist having high sensitivity and high resolution is demanded. Particularly, in order to shorten the wafer processing time, elevation of the sensitivity is very important, but when higher sensitivity is sought for, not only reduction of resolution but also worsening of line edge roughness are brought about, and development of a resist satisfying these properties at the same time is strongly demanded. The line edge roughness as used herein means that the resist edge at the interface between the pattern and the substrate irregularly fluctuates in the direction perpendicular to the line direction due to the resist property and when the pattern is viewed from right above, the edge gives an uneven appearance. This unevenness is transferred by the etching step using the resist as a mask and causes deterioration of electric property, giving rise to decrease in the yield. Above all, in the ultrafine region of 0.25 μm or less, the improvement of line edge roughness is a very important problem to be solved. The high sensitivity is in a trade-off relationship with high resolution, good pattern profile and good line edge roughness, and it is very important how satisfy these requirements at the same time.
In the lithography using X-ray or EUV light, it is also similarly very important to satisfy high sensitivity, high resolution, good pattern profile and good line edge roughness at the same time, and this problem needs to be solved.
As one of the methods for solving these problems, use of a resin having a photo-acid generator (sulfonium group) on the polymer main or side chain is being studied (see, JP-A-2-302758 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-4-230645 and U.S. Pat. No. 5,260,410). However, in the studies of these documents, since the acid generated upon exposure is itself a low molecular monomer, there is a problem in the diffusibility of acid in the resist film, and high resolution and good line edge roughness can be hardly achieved. On the other hand, a polymer combined with an acid that is generated upon exposure is being also studied (see, JP-A-9-325497, JP-A-10-221852, JP-A-2006-178317 and Proc. of SPIE, Vol. 6923, 692312, 2008), but it has not succeeded at present in satisfying all of high sensitivity, high resolution, good pattern profile and good line edge roughness in the ultrafine region.
Furthermore, unlike a conventional light source, in the case of using a light source emitting EUV light, the wavelength of light belongs to an extreme-ultraviolet region and high energy of the light brings about such a prominent outgassing problem that a compound in the resist film is destroyed by fragmentation and volatizes as a low molecular component during exposure to contaminate the environment in the exposure apparatus. Various studies are being made for the reduction of outgassing, and various techniques have been attempted, such as a technique of providing a topcoat layer to suppress volatilization of a low molecular compound (see, for example, European Patent 1,480,078) or a technique of adding a radical trapping agent to suppress decomposition of a polymer (see, for example, U.S. Pat. No. 6,680,157). Efforts for reducing the outgassing are being also exerted in terms of an acid generator (see, JP-A-2007-210904).
In recent years, development of lithography using electron beam, X-ray or EUV light other than excimer laser light is proceeding. Furthermore, the microfabrication using a resist composition is not only used directly for the production of an integrated circuit but is recently also applied to the production or the like of a so-called imprint mold structure (see, for example, JP-A-2004-158287, JP-A-2008-162101 and Yoshihiko Hirai (compiler), Science and New Technology in Nanoimprint, Frontier Publishing (June, 2006)). Accordingly, it is an important task also in using X-ray, soft X-ray or electron beam as an exposure light source to satisfy high sensitivity, high resolution, good pattern profile and good performance in terms of roughness all at the same time, and this task needs to be solved.